1. Field of Invention
This invention relates to the field of dental restorations, particularly implant dentistry. In particular, it relates to interrelating the design of custom abutments and the planning of restorations such as crowns and bridges, to the design of combined abutment-crowns, and to the planning of implant placement.
2. Background
Dental restorations systems seek to provide cosmetic and functional replacements for missing teeth. A dental restorative system that replaces a single tooth typically includes three components: the dental implant fixture, the abutment, and a crown. When more than on tooth is being replaced, a bridge may be used instead of a crown for each replaced tooth.
The dental implant fixture anchors the restorative system to the jawbone. The crown replicates the contour and appearance of the visible portion of the restorative system, to match that of the natural dentition. Finally, the abutment connects the crown to the dental implant fixture. The abutment also holds the crown in proper position and alignment relative to the implant fixture, and absorbs the stress of chewing. Standard methods for preparing dental restorative systems require considerable time, labor and expense. U.S. Pat. No. 6,231,342 explains a standard method involving between six and ten trips of patient to a dentist's office to complete installation of a restorative system. Using more advanced techniques and equipment such as those discussed in U.S. Pat. Nos. 5,674,069, 5,989,029 and 6,231,342, for example, the number of visits to the dentist's office may be reduced, as well as the cost of the restoration. At the same time, the quality of the restoration may be improved. The three-above identified patents teach the design of a custom abutment. In part, measurements are utilized of the position and orientation both of the implant fixture and of the edentulous space. These measurements, along with information about the type of tooth being replaced, allow an abutment and tooth profile to be defined. The abutment approximates the profile of the tooth in reduced size, except in the transition emergence profile region, to match the tooth (i.e., crown) shape with that of the implant.
The abutment must be designed not only to match the tooth profile, but also to meet other constraints such as angular orientation relative to other abutments in the restoration, angular orientation relative to the implant, angle of the emergence profile of the abutment from the implant, the combined thickness of the abutment and crown material, covering of the retaining screw, and so forth. These constraints limit the acceptable abutment and crown designs. These limitations are even more acute in cases where multiple implants are involved and multiple implant replacements limit the range of acceptable restorations.
Consequently, though there has been technology to produce customized abutments, nonetheless substantial manual work has been required to match the requirements of crowns and bridges with those of abutments. Considerable cost savings would be achievable, and the number of patient visits to the dental restoration team reduced, if the design and manufacture of the crown or bridge could be automated (in full or in part), in conjunction with the automation for abutments. Of course, there may be competing and interacting design constraints when both an abutment and a crown are to be designed (and manufactured) concurrently.
A need exists, therefore, for a method and apparatus that will permit automated design and manufacture of abutments, crowns (etc.) and abutment-crown combinations, or other dental restoration components or combinations of components.